p8.1+p8.2

• typical values

  walking: 1m/s or 2.2 mph

  running: 5m/s or 11mph

  cycling: 7m/s or 15 mph

  Olympic cycling: 20m/s or 45 mph
• typical values


  strong wind: 13 m/s or 30 mph

  car: 22m/s or 50 mph

  train: 56m/s or 125 mph

  sound: 330m/s or 758 mph
• thinking distance = speed of car x reaction time
• factors affecting thinking distance

  • alcohol
  • drugs
  • being tired
  • eating + drinking
  • being distracted
  • phone
  • age
• factors affecting breaking distance

  • condition of the brakes
  • road surface [wet, dry, icy]
  • speed of car [faster = longer to break]
• stopping distance = thinking distance + braking distance
• renewable: the source will not be depleted or will be replaced rapidly by natural processes
• non-renewable: the source will run out or will not be replenished in our lifetime
• renewable sources


  • biofuels [wood, ethanol from sugar]
  • solar
  • tidal [underwater currents]
  • wave [on top of the sea]
  • geothermal [hot rocks underground]
  • hydroelectric [dam]
  • wind
• non-renewable sources


  • fossil fuels [coil, oil, gas]
  • nuclear fuels
• nucelar fuels

  • nuclear reactors contain and control nuclear chain reactions that produce heat through fission. that heat is used to make steam that spins a turbine to create electricity.
  • pros: low carbon energy source, safe and reliable
  • cons: non-renewable, can lead to long term health issues, high initial costs.
• fossil fuels

  • fossil fuel power plants burn coals or oil to create heat with is in turn used to generate steam to drive turbines, which egenrate electricity.
  • pros: generate a large amount of electricity, cost-effective, can be found very easily
  • cons: non-renewable, greenhouse gases, releases carbon.
• biofuels


  • biomass is burned to produce high-pressure steam, rotating turbine blades which generate electricity
  • pros: energy efficient, sustainable, no greenhouse gases
  • cons: deforestation and habitat destruction, needs a substantial investment in infrastructure and technology.
• solar


  energy from sunlight is absorbed by the PV cells in the panel. this energy creates electrical charges that move in response to an internal electrical field in the cells, causing electricity to flow.

  pros: renewable, minimal maintenance

  cons: high initial costs, dependant on sunlight
• wind


  • wind turns the propeller-like blades of a turbine around a rotor, which spins a generator which creates electricity.
  • pros: renewable, cost effective
  • cons: birds, dependant on wind
• geothermic


  • geothermic power plants draw fluids from underground reservoirs to the surface to produce heated material.
  • pros: reliable source of power, usable for large and small-scale installations
  • cons: location dependant, high initial costs, can lead to surface instability.
• hydroelectric


  • t the plant level, water flows though a pipe [penstack] and then spins the blades in a turbine, which spins a generator that ultimately generates electricity.
  • pros: renewable energy source, inexpensive in the long-term
  • cons: expensive up-front, some adverse environment impact, lack of available reservoirs.
• waves


  • using turbines that rely on the movement of waves. the bigger the wave, the more kinetic energy which is transferred by the turbines, to generators [ which generate electricity]
  • pros: reliable, 0 emissions, energy potential
  • cons: high costs, scalability, environmental effects,
• tidal


  • turbines inside the barrage enable the basin to fill during incoming tides and release through the system during outgoing tides.
  • pros: more powerful, efficient, renewable
  • cons: initial cost is very high, effect on animals and plants near tidal stations.
• in the national grid, electrical power is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic use.
• power is transferred at lower voltages from the power station to localities because we want the current to be as low as possible to avoid electrocution.

  • to do this, we use a step up transformer for the power station and a step down transformer to the local areas.
• The National Grid system is an efficient way to transfer energy due to its use of high-voltage transmission lines, step-up transformers, and step-down transformers. Large-scale electricity production is often more cost-effective than decentralised small-scale generation, contributing to energy efficiency.
• domestic supply in UK is 230 volts and 50 Hz
• Plugs


  • earth [green and yellow]
  • live [brown]
  • neutral: [blue]
  • the earth pin is a safety feature, excess electricity will go to the ground, taking the danger away.
  • fuses will melt when there is too much electricity. [cheap to replace]
  • 3 core plastic cable, also covered in plastic, avoids electrocution.
• plugs


  live + earth - 230 V

  live + neutral - 230 V

  neutral + earth - O V
• step down transformer decreases potential difference for safety
• step up transformers decrease current to reduce heat losses